The manufacture of semiconductor substrates, or wafers, requires a vacuum environment free of contaminants. Particulate and/or dust generated during handling or processing can destroy a wafer. To reduce the susceptibility of wafers to particulate contamination, it is preferable to process wafers while they are held in vertical orientation.
Applicant's U.S. Pat. No. 4,909,695 discloses a vertical wafer processing apparatus which includes a load/unload station and a plurality of processing stations spaced equidistantly around a horizontal axis. The vertical wafer processing apparatus carrier includes at least one wafer holding ring which holds a wafer in vertical orientation, with preferably one wafer holding ring for each of the stations. To process the wafers, the carrier rotates the wafers successively, in carrousel fashion, to each of the processing stations. One processing step is performed at each station, and the process begins and ends at the load/unload station.
Another type of wafer processing apparatus includes a central horizontal wafer handling module or apparatus connected to a plurality of wafer processing modules which are connectable around the outside of the wafer handling module. The horizontal wafer handling apparatus includes a robot arm which is extendable into any of the other processing modules to transfer a wafer therein for the performance of a desired process on the wafer. With a wafer processing system of this type, versatility in processing various types of wafers is achieved and throughput is increased because the wafer robot can move each wafer into and out of one or more of the modules according to any selected processing sequence. Also, the surrounding processing modules can be changed to suit the particular types of wafer processing needed. Applicant's U.S. Pat. No. 5,154,730 discloses a sputtering module which is connectable to a horizontal wafer handling apparatus of this type.
Unfortunately, for some wafer manufacturing applications, this approach slows down throughput, because only one manufacturing step occurs in each of the modules. While additional modules can be connected to the handler module, or an additional handler module can be added, this increases the overall complexity of the system and also increases space requirements.
It is an objective of this invention to combine the contaminant-free benefits of a vertical wafer processing apparatus with the enhanced versatility in processing capability provided by a horizontal wafer handling apparatus.
It is another objective of the invention to simultaneously achieve a high degree of wafer processing versatility and wafer processing throughout with only minimum space requirements.
The above-stated objectives are met by a wafer transport module which interconnects a horizontal wafer handler with a vertical wafer processor. The wafer transport module of this invention includes a housing which houses a wafer holder and a first port in communication with the horizontal wafer handler and sized to permit passage therethrough of a wafer in horizontal orientation. The wafer transport module also includes a second port in communication with the vertical wafer processor and sized to permit passage therethrough of a wafer in vertical orientation, parallel with a wall of the housing in which the second port is formed.
The wafer holder receives wafers in horizontal orientation from a robot in the horizontal wafer handler, secures the wafer to a horizontal pedestal, rotates the wafer and pedestal about an inclined axis to vertical orientation, and then horizontally extends the vertically held wafer out of the transport module to a load/unload station of the vertical wafer processor.
Because the wafer holder used in this wafer transport module rotates about an inclined axis, one rotational movement moves the wafer from horizontal orientation adjacent the first port to vertical orientation aligned with and adjacent the second port. The wafer holder then horizontally extends the vertically held wafer through the second port and into a load/unload station for transfer to the vertical wafer processor. After wafer processing is complete, the sequence is reversed to return the wafer to the horizontal wafer handler.
This transport module effectively interconnects a horizontal wafer handler with a vertical wafer processor, while occupying only a minimal amount of space. This wafer transport module provides a marriage between a horizontal wafer processing and/or handling system and a vertical wafer processing and/or handling system, thereby enabling a wafer manufacturer to maximize wafer throughput, optimize versatility in selecting a desired sequence of processing steps and also to operate with minimal wafer susceptibility to contamination from particulate.
According to a preferred embodiment of the invention, a wafer transport module for interconnecting a horizontal wafer handling apparatus with a vertical wafer processing apparatus includes an evacuatable housing with first and second ports formed in adjacent side walls thereof. The first port communicates with a horizontal wafer handling apparatus and is sized to permit passage therethrough of a wafer in horizontal orientation. The second port communicates with a load/unload station of a vertical wafer processing apparatus, and the second port is sized to permit passage therethrough of a wafer in vertical orientation and parallel with the side wall through which the second port is formed.
The wafer transport module further includes a wafer holder with a wafer retaining pedestal. The wafer holder is mounted to an inclined turret and rotatable with respect to the turret to move the wafer holder and pedestal between horizontal orientation and vertical orientation, and vise versa. The wafer transport module also includes a piston mounted to a side wall of the housing located opposite the second port. When the wafer holder and pedestal are in vertical orientation and aligned with the second port, the piston horizontally extends and retracts the wafer holder and pedestal through the second port and into the load/unload station of the vertical wafer processing apparatus.
The wafer holder further includes a plurality of pins which are extendable outwardly from and retractable into the pedestal. The pins are carried on a plate located below the pedestal and within the wafer holder. When the pedestal is horizontal and the pins are extended, a wafer may be received on the pins through the first port via a robot arm extended therethrough from the horizontal wafer handler. As the pins retract, the wafer lowers to the pedestal until the backside surface of the wafer is supported thereon.
A plurality of clamps are located radially outside of the pedestal. The clamps move between a radially outward open position and a radially inward closed position. When in the closed position, the clamps engage the front surface of the wafer adjacent its perimeter. When the pins are extended, the clamps are in the open position.
With the wafer retained on the pedestal by the clamps and the pedestal and wafer oriented horizontally and adjacent the first port, the wafer holder may rotate about the inclined axis to move the pedestal and wafer into vertical orientation, in alignment with the second port. Thereafter, the piston horizontally extends the wafer holder, including the pedestal and the wafer retained thereon, through the second port.
Upon horizontal extension through the second port, the front surface of the wafer contacts spring-biased tabs supported by a wafer holding ring carried by the vertical wafer processing apparatus. With the wafer engaged on its front surface by the tabs, a plurality of actuators carried by the wafer holder and located radially outside of the pedestal interact with the wafer holding ring of the vertical wafer processor to rotate rollers held by the ring into engagement with the rear surface of the wafer. The rollers rotate into cutout regions in the side of the pedestal to move behind the wafer without interfering with the pedestal itself. With the wafer held in vertical orientation between the rollers and the tabs of the wafer holding ring, the clamps move radially outwardly to their open positions. The wafer holder ring has internal radially directed notches formed therein to enable the clamps to move radially outwardly without interfering with the wafer holding ring itself. The wafer holder then withdraws into the module. A gate valve may then be closed to isolate the transport module from the vertical wafer processor.
After the first wafer is transferred to the vertical wafer processor, another wafer may be obtained from the horizontal wafer handler and then transferred to the next wafer holding ring of the vertical wafer processor. This process continues until all of the wafer holding rings of the vertical wafer processor hold a wafer.
After processing of a wafer by the vertical processing apparatus is complete, the above-described sequence is reversed. First, with the already processed wafer located at the load/unload station of the vertical wafer processing apparatus, the gate valve is opened. The wafer holder then extends horizontally through the second port to a position adjacent the backside of wafer. The clamps are then radially inwardly closed into contact with the front surface of the wafer. The actuators carried by the wafer holder then rotate the rollers out of contact with the backside surface of the wafer, so that the wafer is held in vertical orientation against the pedestal by the clamps. The wafer holder then horizontally retracts through the second port and into the housing. After retraction, the wafer holder rotates the wafer and the pedestal about the inclined axis from vertical orientation to horizontal orientation and adjacent the first port. The clamps are then moved radially outwardly from the wafer. The plate then moves upwardly to extend the pins and to raise the wafer upwardly from the pedestal, thereby to enable the robot arm to retrieve the wafer back into the horizontal wafer handling apparatus.
Preferably, the timing and sequence of operation for the pins, the clamps, the actuators, rotation of the wafer holder and extension and retraction of the wafer holder are controlled by a single programmable controller. Preferably, this controller is operatively connected to a master controller which coordinates the entire sequence of wafer processing and handling operations performed by the vertical wafer processing apparatus, the wafer transport module and the horizontal wafer handling apparatus, and any other wafer handling and/or processing apparatus or modules interconnected therewith.
These and other features of the invention will be more readily understood in view of the following detailed description and the drawings.